The air interface communications between an access terminal and a radio access network (RAN) may be organized into a protocol stack with a number of different layers. Each layer may perform certain defined functions and may include a defined set of one or more protocols for performing its respective functions. Typically, the lowest layer of the protocol stack is a Physical Layer that defines the frequencies, channel structure, modulation, encoding, etc. used for the wireless communications. Above the Physical Layer, the protocol stack may include a Medium Access Control (MAC) Layer that defines the procedures used to transmit and receive over the “physical layer.” Above the MAC Layer, the protocol stack may include a Connection Layer that controls the use of air interface resources, such as forward traffic channels and reverse traffic channels. Above the Connection Layer, the protocol stack may include a Session Layer that is used to establish and maintain a session between an access terminal and a RAN.
An example of such a protocol stack is described in the specifications for Evolution Data-Optimized (EVDO) communications. In the EVDO approach, an access terminal uses Session Layer protocols to establish a session with a RAN and is then able to use Connection Layer protocols to obtain traffic channels. To establish a session with the RAN, an access terminal may request the RAN to assign it a Unicast Access Terminal Identifier (UATI). The access terminal may also negotiate configuration settings for the session, which may be used for subsequent radio communications between the access terminal and the RAN. Once the session is established, the access terminal may request traffic channels by transmitting a ConnectionRequest message to the RAN that includes the UATI that the RAN assigned to the access terminal.